The present invention relates to a manufacturing method of a die for manufacturing a liquid ejecting head, and a material block used in the method.
Liquid ejecting heads for ejecting pressurized liquid from nozzle orifices in the form of liquid droplets are known and used for various liquids. A typical example of those is an ink jet recording head (refer to Japanese Patent Publication No. 2000-263799A, for example). The ink jet recording head will be described below as an example of the conventional art.
The ink jet recording head (hereinafter referred to as “recording head”) is provided with plural flow passages that correspond to respective nozzle orifices. Each flow passage originates from an ink reservoir, passes a pressure generating chamber, and reaches a nozzle orifice. To satisfy a requirement of downsizing, it is necessary that the pressure generating chambers be formed with a fine pitch that corresponds to a recording density. As a result, each partition that divides the adjoining pressure generating chambers becomes very thin. To efficiently utilize the ink pressure in each pressure generating chamber for ink droplet eject, the flow passage width of an ink supply for connecting the pressure generating chamber with the ink reservoir is smaller than the width of the pressure generating chamber. To form those minute pressure generating chambers and ink supply holes with high dimensional accuracy, the conventional recording head employs a nickel substrate satisfactorily. That is, the pressure generating chambers etc. are formed by performing plastic working on the nickel substrate using a die(s).
Incidentally, as for the die that is used for forming the pressure generating chambers etc. of the conventional recording head, a large number of dies are cut out from a thick die material in such a manner that dies are sequentially cut out one by one, so that a plurality of blank spaces from which the dies are cut out are arrayed so as to form a plurality of arrays in the die material.
In such a case that the blank spaces have to be arranged so as to form the plural arrays, the die material should be large in both lateral and longitudinal directions (the height is in the thickness direction of the material) and hence it is difficult to form, for example, martensitic metal structure (suitable for dies) in the entire die material. This is because in the case of a large die material the cooling rate in a thermal refining process is not uniform in the material, as a result of which portions where martensite is formed normally and portions where martensite and an excessive amount of residual austenite coexist are formed in the single die material. Because of such unevenness in the metal structure distribution, when the dies are cut out as described the above, they include ones that are high in hardness and durability and ones not having such quality. As such, the resulting dies are not uniform in quality.